Combined Solid Solution Engineering Realizes Unprecedented Tunable Broad NIR Emission in Novel Sr 1– z Ba z GeTeO ₆ :Mn ⁴⁺ ( z = 0–1) Phosphors toward Noninvasive Temperature Monitoring

In this work, novel Mn4+-activated Sr1–zBazGeTeO6:0.01 Mn4+ (z = 0–1) phosphors presented recorded broadband NIR emissions (fwhm >100 nm) peaking from 767 to 820 nm in 650 to 1000 nm, upon blue light excitations with increasing z, corresponding to the rare spin-allowed 4T2g→4A2g transition of Mn4+ in a [GeO6] octahedron, which originates from the proposed combined solid solution engineering in this system for the first time. Moreover, temperature sensing performance based on fluorescence lifetime mode is discussed for various samples, showing the maximal relative sensitivity Sr = 3.01% K–1@398 K in a mixed solid solution phase of Sr0.6Ba0.4GeTeO6:0.01 Mn4+. Finally, a film involving a Sr0.4Ba0.6GeTeO6:0.01 Mn4+ phosphor was prepared to use for noninvasive temperature detection in a pork slice. Most encouragingly, this work strongly opens a chapter for finding novel Mn4+-activated broadband NIR-emitting phosphors with tunable emission wavelength over a large range.